This invention relates to a thread pull-off aid of variable geometrical configuration for the overhead drawing-off of a thread from a feed or creel bobbin which is mounted on a bobbin carrier, the geometrical configuration of the pull-off aid being variable by a control pulse which is dependent directly or indirectly upon the decreasing diameter of the creel bobbin.
In the case of a disc-shaped pull-off aid of this kind in which is described in German Patent Specification No. 30 29 598, corresponding to U.S. Pat. No. 4,502,644, and whose disc comprises segments which are radially displaceable with respect to its diameter, the weight or the diameter of the feed or creel bobbin, or alternatively, the elapsed time during which pull-off from the bobbin has taken place, is used as a control variable or, alternatively, as a control pulse for the radial displacement.
The present invention resides in a pull-off aid of variable geometrical configuration for the overhead drawing-off of a thread, to be wound onto a bobbin, from a feed or creel bobbin mounted on a bobbin carrier, the pull-off aid having a geometrical configuration which is variable by a control pulse and a diameter sensor being provided for sensing the diameter of the bobbin being wound to produce the said control pulse when the bobbin being wound has a predetermined diameter, whereby the configuration of the pull-off aid is dependent on the diameter of the feed or creel bobbin.
If considerations are based on the fact that, with respect to its state, the variable pull-off aid is to be varied to a new, smaller diameter when the feed or creel bobbins are approximately at half their diameter, the same applies to the bobbin being wound, since the latter will at the same instant have reached a specific precalculable diameter. Hence, the bobbin being wound has an associated diameter sensor by which the control pulse varying the pull-off aid is triggered when the bobbin being wound reaches a predetermined diameter.